STMOD_CELLULAR: add DISCO_L562_QE support

Author: jeromecoutant

components/cellular/COMPONENT_STMOD_CELLULAR/README.md

@@ -121,6 +121,24 @@ Default HW configuration:
 
 BG96 expansion board can be used but without flow control.
 
+### DISCO_L562_QE
+
+https://os.mbed.com/platforms/ST-Discovery-L562QE/
+
+HW configuration:
+
+Depending on PF_11 and PF_12 GPIO configuration, STMOD pins 1, 2, 3 and 4 can be mapped to SPI3 or UART3.
+
+STModCellular default init procedure is setting the correct values in order to get full UART connectivity.
+
+See in mbed-trace:
+```
+[INFO][STMOD]: STModCellular creation
+[INFO][STMOD]: STMOD+ UART pins re-configuration
+```
+
+BG96 expansion board is then fully compatible.
+
 ### DISCO_H747I
 
 https://os.mbed.com/platforms/ST-Discovery-H747I/

components/cellular/COMPONENT_STMOD_CELLULAR/STModCellular.cpp

@@ -24,6 +24,10 @@
 using namespace mbed;
 
 STModCellular::STModCellular(FileHandle *fh) : STMOD_CELLULAR_MODEM(fh),
+#if defined(TARGET_DISCO_L562QE)
+    STMOD_SEL_12(PF_11),
+    STMOD_SEL_34(PF_12),
+#endif
     m_powerkey(MBED_CONF_STMOD_CELLULAR_POWER),
     m_reset(MBED_CONF_STMOD_CELLULAR_RESET),
     m_simsel0(MBED_CONF_STMOD_CELLULAR_SIMSEL0),
@@ -35,6 +39,13 @@ STModCellular::STModCellular(FileHandle *fh) : STMOD_CELLULAR_MODEM(fh),
 {
     tr_info("STModCellular creation");
 
+#if defined(TARGET_DISCO_L562QE)
+    /* See PinNames.h file, STMOD+ pins are configurable */
+    STMOD_SEL_12 = 1;
+    STMOD_SEL_34 = 1;
+    tr_info("STMOD+ UART pins re-configuration");
+#endif
+
     // start with modem disabled
     m_powerkey.write(0);
     m_reset.write(1);

components/cellular/COMPONENT_STMOD_CELLULAR/STModCellular.h

@@ -48,6 +48,10 @@ class STModCellular : public STMOD_CELLULAR_MODEM {
     DigitalIn m_sim_reset;
     DigitalIn m_sim_clk;
     DigitalIn m_sim_data;
+#if defined(TARGET_DISCO_L562QE)
+    DigitalOut STMOD_SEL_12;
+    DigitalOut STMOD_SEL_34;
+#endif
 public:
     STModCellular(FileHandle *fh);
     virtual nsapi_error_t soft_power_on();

components/cellular/COMPONENT_STMOD_CELLULAR/mbed_lib.json

@@ -69,6 +69,9 @@
     "target_overrides": {
         "DISCO_L4R9I": {
             "rts": "NC"
+        },
+        "DISCO_L562QE": {
+            "rts": "PD_2"
         }
     }
 }